This invention relates to novel compounds exhibiting a liquid crystal phase and liquid crystal compositions comprising the same.
Liquid crystal display elements are obtained by utilizing the optical anisotropy and dielectric anisotropy of liquid crystal substances, and if those which have now been practically used are classified in a principle manner, TN type (twisted nematic type), DS type (dynamic scattering type), guest-host type, PC type (phase transition type), DAP type, etc. are representative. Properties of liquid crystal substances suitable to the uses of the respective types vary, but any of the liquid crystal substances are common in that they require stabilities to moisture, air and physical effects such as heat, radiations at infrared part, visible part and ultraviolet part, and continuous and alternate electric field. Further, as commercially usable liquid crystal materials, those which can be existent in the form of liquid crystal phase at a temperature range of 0.degree. C. to 60.degree. C. are preferred. Furthermore, there are the optimal values of physical properties which vary depending on the kinds of display elements (anistropy of dielectric constant and anisotropy of refractive index). In the present status, no single compound which satisfies these various performances is present, and liquid crystal compositions obtained by mixing some kinds of liquid-crystalline compounds or non-liquid-crystalline compounds have been practically used.
The object of the present invention is to provide compounds which are useful as a component constituting such liquid crystal compositions and particularly capable of broadening their liquid crystal temperature range due to high clearing point of the compounds.